U.S. patent application number 13/652677 was filed with the patent office on 2013-06-27 for composition for an oxide thin film, a preparation method of the composition, a method for forming an oxide thin film using the composition, an electronic device including the oxide thin film, and a semiconductor device including the oxide thin film.
This patent application is currently assigned to Industry-Academic Cooperation Foundation, Yonsei University. The applicant listed for this patent is Industry-Academic Cooperation Foundation, Yons. Invention is credited to Woong Hee JEONG, Hyun Jae KIM, You Seung RIM.
Application Number | 20130161620 13/652677 |
Document ID | / |
Family ID | 48653633 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130161620 |
Kind Code |
A1 |
KIM; Hyun Jae ; et
al. |
June 27, 2013 |
COMPOSITION FOR AN OXIDE THIN FILM, A PREPARATION METHOD OF THE
COMPOSITION, A METHOD FOR FORMING AN OXIDE THIN FILM USING THE
COMPOSITION, AN ELECTRONIC DEVICE INCLUDING THE OXIDE THIN FILM,
AND A SEMICONDUCTOR DEVICE INCLUDING THE OXIDE THIN FILM
Abstract
Provided are a composition for an oxide thin film, a preparation
method of the composition, a method for forming an oxide thin film
using the composition, an electronic device including the oxide
thin film, and a semiconductor device including the oxide thin
film. The composition for the oxide thin film includes a metal
precursor and nitric acid-based stabilizer. The metal precursor
includes at least one of a metal nitrate, a metal nitride, and
hydrates thereof.
Inventors: |
KIM; Hyun Jae; (Seoul,
KR) ; JEONG; Woong Hee; (Seoul, KR) ; RIM; You
Seung; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Industry-Academic Cooperation Foundation, Yons; |
Seoul |
|
KR |
|
|
Assignee: |
Industry-Academic Cooperation
Foundation, Yonsei University
Seoul
KR
|
Family ID: |
48653633 |
Appl. No.: |
13/652677 |
Filed: |
October 16, 2012 |
Current U.S.
Class: |
257/57 ;
252/519.3; 252/519.5; 252/521.5; 257/E21.09; 257/E29.273;
438/479 |
Current CPC
Class: |
H01L 21/02554 20130101;
H01L 21/02565 20130101; H01L 21/02628 20130101; H01L 29/66742
20130101 |
Class at
Publication: |
257/57 ; 438/479;
252/521.5; 252/519.5; 252/519.3; 257/E21.09; 257/E29.273 |
International
Class: |
H01B 1/06 20060101
H01B001/06; H01L 29/786 20060101 H01L029/786; H01B 1/12 20060101
H01B001/12; H01L 21/20 20060101 H01L021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2011 |
KR |
10-2011-0143833 |
Claims
1. A composition for an oxide thin film, comprising: a metal
precursor including at least one of a metal nitrate, a metal
nitride, and hydrates thereof; and a nitric acid-based
stabilizer.
2. The composition of claim 1, wherein the nitric acid-based
stabilizer includes at least one of nitric acid and ammonium
nitrate.
3. The composition of claim 1, wherein a metal of the metal
precursor includes at least one of zinc, indium, tin, gallium,
hafnium, magnesium, aluminum, yttrium, tantalum, titanium,
zirconium, barium, lanthanum, manganese, tungsten, molybdenum,
cerium, chromium, scandium, silicon, neodymium, and strontium.
4. The composition of claim 3, further comprising: a solvent
capable of dissolving the metal precursor, wherein the solvent
includes at least one of isopropanol, 2-methoxyethanol,
dimethylformaldehyde, ethanol, deionized water, methanol,
acetylacetone, dimethylamineborane, and acetonitrile.
5. The composition of claim 4, wherein a molar ratio of the nitric
acid-based stabilizer to the metal precursor is 1:1 to 10:1.
6. The composition of claim, 5, wherein the metal precursor
includes an indium precursor and a zinc precursor; and wherein a
molar ratio of the indium precursor to the zinc precursor is 1:1 to
9:1.
7. The composition of claim 4, wherein a molar concentration of the
metal precursor is 0.1M to 10M.
8. The composition of claim 7, wherein a molar ratio of the nitric
acid-based stabilizer to the metal precursor is 1:1 to 10:1.
9. The composition of claim 1, further comprising: a solvent
capable of dissolving the metal precursor, wherein the solvent
includes at least one of isopropanol, 2-methoxyethanol,
dimethylformaldehyde, ethanol, deionized water, methanol,
acetylacetone, dimethylamineborane, and acetonitrile.
10. The composition of claim 9, wherein a molar ratio of the nitric
acid-based stabilizer to the metal precursor is 1:1 to 10:1.
11. The composition of claim 10, wherein a molar concentration of
the metal precursor is 0.1M to 10M.
12. A method for forming an oxide thin film, comprising: depositing
a composition for the oxide thin film on a substrate, the
composition including a metal precursor and a nitric acid-based
stabilizer, the metal precursor including at least one of metal
nitrate, metal nitride, and hydrates thereof; and annealing the
substrate having the coated composition at a temperature of
100.degree. C. to 450.degree. C.
13. The method of claim 12, wherein annealing the substrate is
performed at a temperature of 200.degree. C. to 300.degree. C.
14. The method of claim 13, wherein depositing the composition for
the oxide thin film on the substrate comprises: depositing the
composition for the oxide thin film on a flexible substrate or a
glass substrate.
15. An electronic device comprising: an oxide thin film formed by
the method of claim 12; a gate electrode disposed on the oxide thin
film; and a source electrode and a drain electrode electrically
connected to the oxide thin film and disposed at both sides of the
gate electrode, respectively.
16. A semiconductor device comprising: an oxide thin film formed on
a flexible substrate or a glass substrate, wherein the oxide thin
film is formed by the method of claim 12.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This U.S. non-provisional patent application claims priority
under 35 U.S.C. .sctn.119 to Korean Patent Application No.
10-2011-0143833, filed on Dec. 27, 2011, the entirety of which is
incorporated by reference herein.
BACKGROUND
[0002] Embodiments according to the inventive concept relate to a
composition for an oxide thin film, a method for forming the oxide
thin film using the composition, an electronic device including the
oxide thin film, and a semiconductor device including the thin
oxide film.
[0003] Recently, various researches have been conducted for an
oxide semiconductor substituting for a silicon-based semiconductor
device. A binary oxide and/or ternary oxide compounds based on
indium oxide (In.sub.2O.sub.3), zinc oxide (ZnO) and/or gallium
oxide (Ga.sub.2O.sub.3) have been developed as the oxide
semiconductor in a material aspect. In a process aspect, a solution
process instead of a conventional vacuum deposition process has
been developed for the oxide semiconductor.
[0004] The oxide semiconductor may exhibit an amorphous state as
hydrogenated amorphous silicon. However, since the oxide
semiconductor has more excellent mobility (5-10 cm.sup.2/Vs) than
the hydrogenated amorphous silicon, the oxide semiconductor may be
suitable for a high-definition liquid crystal display (LCD), an
active matrix organic light emitting diode (AMOLED) display, etc.
Additionally, a manufacture technique of the oxide semiconductor
using the solution process has a lower costs characteristic than
the vacuum deposition process of high costs. However, a method of
forming the oxide thin film using a conventional solution process
needs a high temperature-annealing process of 450.degree. C. or
more. It is difficult to apply the annealing process of 450.degree.
C. or more to a 8.sup.th generation or more of a large glass
substrate as well as a plastic substrate.
SUMMARY
[0005] Embodiments of the inventive concept may provide a method of
forming an oxide semiconductor using a low temperature process, a
composition for the same, an oxide semiconductor device formed by
the low temperature process, and an electronic device including
oxide semiconductor.
[0006] In one aspect, a composition for an oxide thin film
includes: a metal precursor including at least one of a metal
nitrate, a metal nitride, and hydrates thereof; and a nitric
acid-based stabilizer.
[0007] In another aspect, a method for forming an oxide thin film
includes: depositing a composition for the oxide thin film on a
substrate, the composition including a metal precursor and a nitric
acid-based stabilizer, and the metal precursor including at least
one of metal nitrate, metal nitride, and hydrates thereof; and
annealing the substrate having the coated composition at a
temperature within a range of 100.degree. C. to 450.degree. C.
[0008] In still another aspect, an electronic device includes: an
oxide thin film formed by the method for forming the oxide thin
film; a gate electrode disposed on the oxide thin film; and a
source electrode and a drain electrode electrically connected to
the oxide thin film and disposed at both sides of the gate
electrode, respectively.
[0009] In yet another aspect, a semiconductor device includes: an
oxide thin film formed on a flexible substrate or a glass substrate
by the method for forming the oxide thin film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The inventive concept will become more apparent in view of
the attached drawings and accompanying detailed description.
[0011] FIG. 1 shows a transfer curve and an output curve of a InZnO
thin film transistor manufactured under an annealing process of
300.degree. C. according to a first embodiment of the inventive
concept;
[0012] FIG. 2 shows a result of an x-ray photoelectron spectroscopy
(XPS) measurement of a InZnO thin film formed using a nitric acid
stabilizer according to a first embodiment of the inventive concept
and a result of a comparison XPS of residual organic materials
within InZnO thin films formed by stabilizers different from each
other;
[0013] FIG. 3 shows transfer curves of InZnO thin film transistors
which are formed using an InZnO solution of a first embodiment
under an annealing process of 250.degree. C. by annealing
apparatuses different from each other, respectively;
[0014] FIG. 4 shows mobility of thin film transistors formed by
changing a molar ratio of zinc to indium;
[0015] FIG. 5 shows an electrical characteristic curve of an
aluminum oxide thin film which is formed by a precursor solution of
a third embodiment and a high-pressure annealing process performed
under an oxygen atmosphere at a temperature of 250.degree. C.;
[0016] FIG. 6 shows an electrical characteristic curve of a thin
film transistor which includes the aluminum oxide thin film of FIG.
5 used as a gate insulating layer, and an oxide semiconductor
formed using an IZO solution of a first embodiment and stacked on
the aluminum oxide thin film;
[0017] FIG. 7 shows electrical characteristic curves of a thin film
transistor formed by a second embodiment and a thin film transistor
formed by a comparison embodiment;
[0018] FIG. 8 shows electrical characteristic curves of thin film
transistors formed using solutions which are formed by controlling
a composition ratio of indium to zinc in a second embodiment within
a range of 1:1 to 10:0; and
[0019] FIG. 9 shows a test result of stability with respect to a
remaining time of a thin film transistor formed by an oxide
solution having a composition ratio of indium to zinc of 5:1 and
not applied with a passivation layer.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0020] The inventive concept will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the inventive concept are shown. The
advantages and features of the inventive concept and methods of
achieving them will be apparent from the following exemplary
embodiments that will be described in more detail with reference to
the accompanying drawings. It should be noted, however, that the
inventive concept is not limited to the following exemplary
embodiments, and may be implemented in various forms. Accordingly,
the exemplary embodiments are provided only to disclose the
inventive concept and let those skilled in the art know the
category of the inventive concept. In the drawings, embodiments of
the inventive concept are not limited to the specific examples
provided herein and are exaggerated for clarity.
[0021] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to limit the
invention. As used herein, the singular terms "a," "an" and "the"
are intended to include the plural forms as well, unless the
context clearly indicates otherwise. As used herein, the term
"and/or" includes any and all combinations of one or more of the
associated listed items. It will be understood that when an element
is referred to as being "connected" or "coupled" to another
element, it may be directly connected or coupled to the other
element or intervening elements may be present.
[0022] Similarly, it will be understood that when an element such
as a layer, region or substrate is referred to as being "on"
another element, it can be directly on the other element or
intervening elements may be present. In contrast, the term
"directly" means that there are no intervening elements. It will be
further understood that the terms "comprises", "comprising,",
"includes" and/or "including", when used herein, specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.
[0023] Additionally, the embodiment in the detailed description
will be described with sectional views as ideal exemplary views of
the inventive concept. Accordingly, shapes of the exemplary views
may be modified according to manufacturing techniques and/or
allowable errors. Therefore, the embodiments of the inventive
concept are not limited to the specific shape illustrated in the
exemplary views, but may include other shapes that may be created
according to manufacturing processes. Areas exemplified in the
drawings have general properties, and are used to illustrate
specific shapes of elements. Thus, this should not be construed as
limited to the scope of the inventive concept.
[0024] It will be also understood that although the terms first,
second, third etc. may be used herein to describe various elements,
these elements should not be limited by these terms. These terms
are only used to distinguish one element from another element.
Thus, a first element in some embodiments could be termed a second
element in other embodiments without departing from the teachings
of the present invention. Exemplary embodiments of aspects of the
present inventive concept explained and illustrated herein include
their complementary counterparts. The same reference numerals or
the same reference designators denote the same elements throughout
the specification.
[0025] Moreover, exemplary embodiments are described herein with
reference to cross-sectional illustrations and/or plane
illustrations that are idealized exemplary illustrations.
Accordingly, variations from the shapes of the illustrations as a
result, for example, of manufacturing techniques and/or tolerances,
are to be expected. Thus, exemplary embodiments should not be
construed as limited to the shapes of regions illustrated herein
but are to include deviations in shapes that result, for example,
from manufacturing. For example, an etching region illustrated as a
rectangle will, typically, have rounded or curved features. Thus,
the regions illustrated in the figures are schematic in nature and
their shapes are not intended to illustrate the actual shape of a
region of a device and are not intended to limit the scope of
example embodiments.
[0026] A method of forming the oxide thin film using a conventional
solution process needs a high temperature-annealing process of
450.degree. C. or more. It is difficult to apply the annealing
process of 450.degree. C. or more to a 8.sup.th generation or more
of a large glass substrate as well as a plastic substrate.
[0027] Thus, embodiments of the inventive concept suggest or
develop a method for forming an electronic device applied with an
oxide material which is performed under a temperature (e.g., about
450.degree. C. or less) capable of being applied to a large area
glass substrate or plastic substrate by controlling a precursor of
a composition for an oxide thin film and/or by controlling a
stabilizer.
[0028] Composition for Oxide Thin Film
[0029] A composition for an oxide thin film according to some
embodiments of the inventive concept includes a metal precursor
proving an oxide thin film source and a stabilizer. The metal
precursor may be easily dissolved in a solvent by the stabilizer.
In some embodiments of the inventive concept, a nitric acid-based
stabilizer is used as the stabilizer. The nitric acid-based
stabilizer promotes evaporation of a solution and decomposition of
the metal precursor. And the nitric acid-based stabilizer promotes
oxidation and hydration. The nitric acid-based stabilizer enables
the formation of a good quality and pure oxide thin film not
including carbon. The nitric acid-based stabilizer according to the
inventive concept enable the good quality oxide thin film to be
formed by an annealing process of a low temperature, for example,
within a range of about 100.degree. C. to about 450.degree. C.
Particularly, the low temperature may be within a range of about
200.degree. C. to about 300.degree. C. More particularly, the low
temperature may be about 200.degree. C. or less.
[0030] In some embodiments of the inventive concept, nitric acid
and/or ammonium nitrate may be used as the nitric acid-based
stabilizer. However, the inventive concept is not limited thereto.
Particularly, the nitric acid may be used as the nitric acid-based
stabilizer.
[0031] A metal in the metal precursor according to some embodiment
of the inventive concept may include at least one of zinc, indium,
tin, gallium, hafnium, magnesium, aluminum, yttrium, tantalum,
titanium, zirconium, barium, lanthanum, manganese, tungsten,
molybdenum, cerium, chromium, scandium, silicon, neodymium, and
strontium.
[0032] The solvent dissolving the metal precursor according to some
embodiments of the inventive concept may include at least one of
isopropanol, 2-methoxyethanol, dimethylformaldehyde, ethanol,
deionized water, methanol, acetylacetone, dimethylamineborane, and
acetonitrile.
[0033] Various materials may be used as the metal precursor.
Particularly, the metal precursor may include at least one of metal
nitrate, metal nitride and hydrates thereof.
[0034] Zinc salts and hydrates thereof may be used as a zinc
precursor. However, the inventive concept is not limited thereto.
For example, the zinc precursor may include at least one of zinc
nitrate, zinc nitride, zinc citrate dihydrate, zinc acetate, zinc
acetate dihydrate, zinc acetylacetonate hydrate, zinc acrylate,
zinc chloride, zinc diethyldithiocarbamate, zinc
dimethyldithiocarbamate, zinc fluoride, zinc fluoride hydrate, zinc
hexafluoroacetylacetonate dihydrate, zinc methacrylate, zinc
nitrate hexahydrate, zinc nitrate hydrate, zinc
trifluoromethanesulfonate, zinc undecylenate, zinc trifluoroacetate
hydrate, zinc tetrafluoroborate hydrate, zinc perchlorate
hexahydrate, and hydrates thereof. Particularly, at least one of
zinc nitrate, zinc nitride, and hydrates thereof may be used as the
zinc precursor.
[0035] An indium precursor may include at least one of indium salts
and hydrates thereof. However, the inventive concept is not limited
thereto. For example, the indium precursor may include at least one
of indium nitrate, indium nitride, indium Chloride, indium chloride
tetrahydrate, indium fluoride, indium fluoride trihydrate, indium
hydroxide, indium nitrate hydrate, indium acetate hydrate, indium
acetylacetonate, indium acetate, and hydrates thereof.
Particularly, at least one of indium nitrate, indium nitride, and
hydrates thereof may be used as the indium precursor.
[0036] A tin precursor may include at least one of tin salts and
hydrates thereof. However, the inventive concept is not limited
thereto. For example, the tin precursor may include at least one of
tin nitrate, tin nitride, tin(II) chloride, tin(II) iodide, tin(II)
chloride dihydrate, tin(II) bromide, tin(II) fluoride, tin(II)
oxalate, tin(II) sulfide, tin(II) acetate, tin(IV) chloride,
tin(IV) chloride pentahydrate, tin(IV) fluoride, tin(IV) iodide,
tin(IV) sulfide, tin(IV) tert-butoxide, and hydrates thereof.
Particularly, at least one of tin nitrate, tin nitride, and
hydrates thereof may be used as the tin precursor.
[0037] A gallium precursor may include at least one of gallium
salts and hydrates thereof. The inventive concept is not limited
thereto. For example, the gallium precursor may include at least
one of gallium nitrate, gallium nitride, gallium phosphide,
gallium(II) chloride, gallium(III) acetylacetonate, gallium(III)
bromide, gallium(III) chloride, gallium(III) fluoride, gallium(III)
iodide, gallium(III) nitrate hydrate, gallium(III) sulfate,
gallium(III) sulfate hydrate, and hydrates thereof. Particularly,
at least one of gallium nitrate, gallium nitride, and hydrates
thereof may be used as the gallium precursor.
[0038] A zirconium precursor may include at least one of zirconium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the zirconium precursor may include
at least one of zirconium nitrate, zirconium nitride, zirconium
acetate, zirconium(II) hydride, zirconium(IV) acetate hydroxide,
zirconium(IV) acetylacetonate, zirconium(IV) butoxide solution,
zirconium(IV) carbide, zirconium(IV) chloride, zirconium(IV)
ethoxide, zirconium(IV) fluoride, zirconium(IV) fluoride hydrate,
zirconium(IV) hydroxide, zirconium(IV) iodide, zirconium(IV)
sulfate hydrate, zirconium(IV) tert-butoxide, and hydrates thereof.
Particularly, at least one of zirconium nitrate, zirconium nitride,
and hydrates thereof may be used as the zirconium precursor.
[0039] An aluminum precursor may include at least one of aluminum
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the aluminum precursor may include at
least one of aluminum nitrate, aluminum nitride, aluminum acetate,
aluminum acetylacetonate, aluminum borate, aluminum bromide,
aluminum carbide, aluminum chloride, aluminum chloride hexahydrate,
aluminum chloride hydrate, aluminum ethoxide, aluminum fluoride,
aluminum hydroxide hydrate, aluminum iodide, aluminum isopropoxide,
aluminum nitrate nonahydrate, aluminum nitride, aluminum phosphate,
aluminum sulfate, aluminum sulfate hexadecahydrate, aluminum
sulfate hydrate, aluminum tert-butoxide, and hydrates thereof.
Particularly, at least one of aluminum nitrate, aluminum nitride,
and hydrates thereof may be used as the aluminum precursor.
[0040] A neodymium precursor may include at least one of neodymium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the neodymium precursor may include
at least one of neodymium nitrate, neodymium nitride, neodymium(II)
iodide, neodymium(III) acetate hydrate, neodymium(III)
acetylacetonate hydrate, neodymium(III) bromide, neodymium(III)
bromide hydrate, neodymium(III) carbonate hydrate, neodymium(III)
chloride, neodymium(III) chloride hexahydrate, neodymium(III)
fluoride, neodymium(III) hydroxide hydrate, neodymium(III) iodide,
neodymium(III) isopropoxide, neodymium(III) nitrate hexahydrate,
neodymium(III) nitrate hydrate, neodymium(III) oxalate hydrate,
neodymium(III) phosphate hydrate, neodymium(III) sulfate,
neodymium(III) sulfate hydrate, and hydrates thereof. Particularly,
at least one of neodymium nitrate, neodymium nitride, and hydrates
thereof may be used as the neodymium precursor.
[0041] A scandium precursor may include at least one of scandium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the scandium precursor may include at
least one of scandium nitrate, scandium nitride, scandium acetate
hydrate, scandium acetylacetonate hydrate, scandium chloride,
scandium chloride hexahydrate, scandium chloride hydrate, scandium
fluoride, scandium nitrate hydrate, and hydrates thereof.
Particularly, at least one of scandium nitrate, scandium nitride,
and hydrates thereof may be used as the scandium precursor.
[0042] A tantalum precursor supplying tantalum may include at least
one of tantalum salts and hydrates thereof. However, the inventive
concept is not limited thereto. For example, the tantalum precursor
may include at least one of tantalum bromide, tantalum chloride,
tantalum fluoride, and hydrates thereof.
[0043] A titanium precursor may include at least one of titanium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the titanium precursor may include at
least one of titanium nitrate, titanium nitride, titanium bromide,
titanium chloride, titanium fluoride, and hydrates thereof.
Particularly, at least one of titanium nitrate, titanium nitride,
and hydrates thereof may be used as the titanium precursor.
[0044] A barium precursor may include at least one of barium salts
and hydrates thereof. However, the inventive concept is not limited
thereto. For example, the barium precursor may include at least one
of barium nitrate, barium nitride, barium acetate, barium
acetylacetonate, barium bromide, barium chloride, barium fluoride,
barium hexafluoacetylacetonate, barium hydroxide, and hydrates
thereof. Particularly, at least one of barium nitrate, barium
nitride, and hydrates thereof may be used as the barium
precursor.
[0045] A lanthanum precursor may include at least one of lanthanum
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the lanthanum precursor may include
at least one of lanthanum nitrate, lanthanum nitride, lanthanum
acetate, lanthanum acetylacetonate, lanthanum bromide, lanthanum
chloride, lanthanum hydroxide, lanthanum fluoride, and hydrates
thereof. Particularly, at least one of lanthanum nitrate, lanthanum
nitride, and hydrates thereof may be used as the lanthanum
precursor.
[0046] A manganese precursor may include at least one of manganese
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the manganese precursor may include
at least one of manganese nitrate, manganese nitride, manganese
acetate, manganese acetylacetonate, manganese bromide, manganese
chloride, manganese fluoride, and hydrates thereof. Particularly,
at least one of manganese nitrate, manganese nitride, and hydrates
thereof may be used as the manganese precursor.
[0047] A chromium precursor may include at least one of chromium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the chromium precursor may include at
least one of chromium nitrate, chromium nitride, chromium acetate,
chromium acetylacetonate, chromium bromide, chromium chloride,
chromium fluoride, and hydrates thereof. Particularly, at least one
of chromium nitrate, chromium nitride, and hydrates thereof may be
used as the chromium precursor.
[0048] A strontium precursor may include at least one of strontium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the strontium precursor may include
at least one of strontium nitrate, strontium nitride, strontium
acetate, strontium acetylacetonate, strontium bromide, strontium
chloride, strontium fluoride, strontium hydroxide, and hydrates
thereof. Particularly, at least one of strontium nitrate, strontium
nitride, and hydrates thereof may be used as the strontium
precursor.
[0049] An yttrium precursor may include at least one of yttrium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the yttrium precursor may include at
least one of yttrium nitrate, yttrium nitride, yttrium acetate,
yttrium acetylacetonate, yttrium chloride, yttrium fluoride, and
hydrates thereof. Particularly, at least one of yttrium nitrate,
yttrium nitride, and hydrates thereof may be used as the yttrium
precursor.
[0050] A cerium precursor may include at least one of cerium salts
and hydrates thereof. However, the inventive concept is not limited
thereto. For example, the cerium precursor may include at least one
of cerium nitrate, cerium nitride, cerium(III) acetate hydrate,
cerium(III) acetylacetonate hydrate, cerium(III) bromide,
cerium(III) carbonate hydrate, cerium(III) chloride, cerium(III)
chloride heptahydrate, cerium(III) fluoride, cerium(III) iodide,
cerium(III) nitrate hexahydrate, cerium(III) oxalate hydrate,
cerium(III) sulfate, cerium(III) sulfate hydrate, cerium(III)
sulfate octahydrate, cerium(IV) fluoride, cerium(IV) hydroxide,
cerium(IV) sulfate, cerium(IV) sulfate hydrate, cerium(IV) sulfate
tetrahydrate, and hydrates thereof. Particularly, at least one of
cerium nitrate, cerium nitride, and hydrates thereof may be used as
the cerium precursor.
[0051] A hafnium precursor may include at least one of hafnium
salts and hydrates thereof. However, the inventive concept is not
limited thereto. For example, the hafnium precursor may include at
least one of hafnium nitrate, hafnium nitride, hafnium chloride,
hafnium fluoride, and hydrates thereof. Particularly, at least one
of hafnium nitrate, hafnium nitride, and hydrates thereof may be
used as the hafnium precursor.
[0052] A silicon precursor may include at least one of silicon
nitride, silicon tetraacetate, silicon tetrabromice, silicon
tetrachloride, and silicon tetrafluoride. Particularly, silicon
nitride may be used as the silicon precursor.
[0053] According to some embodiments of the inventive concept, the
composition for the oxide thin film may include the aforementioned
nitric acid-based stabilizer and any combination of the
aforementioned metal precursors. Kinds of the metal precursors may
be suitably selected to obtain desired electrical characteristics
of the oxide thin film. In other words, the oxide thin film may be
a conductor, a semiconductor, or an insulator according to the kind
of the metal precursor.
[0054] For example, if zinc nitrate and indium nitrate are used as
the metal precursor, the formed oxide thin film may be used as a
channel layer of a thin film transistor. On the other hand, if
aluminum nitrate is used as the metal precursor, the formed oxide
thin film may be used as a gate insulating layer of a thin film
transistor.
[0055] Thus, in some embodiments, if the metal precursor is
suitably controlled, the channel layer and the gate insulating
layer may be formed simultaneously or sequentially formed by the
solution process.
[0056] Additionally, if a composition ratio (e.g., a molar ratio,
an atomic number ratio, and/or a molar concentration ratio) between
the metal precursors is suitably controlled, it is possible to form
the thin film transistor having a desired characteristic (showing a
desired characteristic curve).
[0057] For example, a molar concentration of the metal precursor
may be within a range of about 0.1M to about 10M.
[0058] For example, if the indium precursor and the zinc precursor
are used as the metal precursor, the molar ratio of the indium
precursor to the zinc precursor may be within a range of 1:1 to
9:1.
[0059] For example, the nitric acid-based stabilizer may have the
same molar concentration as the metal precursor in the composition
for the oxide thin film.
[0060] For example, a molar ratio of the nitric acid-based
stabilizer to the metal precursor may be within a range of 1:1 to
10:1.
[0061] Coating and Annealing
[0062] The composition for the oxide thin film may be deposited on
a substrate by a screen printing method, a spin coating method, a
dip coating method, a spray method, roll-to-roll method, and/or
ink-jet method.
[0063] After the composition for the oxide thin film is deposited
on the substrate, an annealing process for the formation of the
oxide thin film may use a furnace, a hot plate, and/or a rapid
thermal annealing process. An atmosphere of the annealing process
may be applied with a general air atmosphere, a vacuum atmosphere,
a vapor atmosphere, a nitrogen atmosphere, a hydrogen atmosphere,
an oxygen atmosphere, a reduction atmosphere, and/o be a
pressurized atmosphere. The annealing process may be a laser
annealing process, an ultraviolet ray (UV) annealing process,
and/or a plasma annealing process.
[0064] The substrate on which the composition for the oxide thin
film is coated may be selected from various kinds of substrates
such as a silicon substrate, a plastic substrate, a glass
substrate, and a flexible substrate according to application
fields.
First Embodiment: Precursor Solution for IZO(InGaZnO) Thin Film
[0065] 2-methoxyethnal, indium nitrate hydrate, zinc nitrate, and
nitric acid were prepared. The 2-methoxyethnal was used as a
solvent. The indium nitrate hydrate and zinc nitrate were used as
the precursor solution. The nitric acid was used as a stabilizer. A
composition ratio of indium to zinc was 3:1 (i.e., the molar ratio
of the indium nitrate hydrate to zinc nitrate was 3:1). The molar
concentration of the precursor solution was 0.3M. After the indium
nitrate hydrate and the zinc nitrate were mixed and the solvent was
added to the mixed solution as to satisfy the molar ratio and the
molar concentration. Thereafter, the nitric acid of the same molar
concentration as the precursor solution was added to the solution
having the precursor solution and the solvent. The resultant mixed
solution for the oxide thin film was stirred at a temperature of
about 50.degree. C. at 300 rpm for 1 hour. The stirred oxide
solution was stabilized for about a day.
Second Embodiment: Precursor Solution for IZO(InZnO) Thin Film
[0066] The composition ratio of indium to zinc was variously
changed within a range of 1:1 to 10:1 to form precursor solutions
by the same method as the first embodiment.
Third Embodiment: Precursor Solution for AlO Thin Film
[0067] 2-methoxyethnal, aluminum nitrate and nitric acid were
prepared. The 2-methoxyethnal was used as a solvent, the aluminum
nitrate was used as a precursor solution, and the nitric acid was
used as a stabilizer. The precursor solution was added into
2-methoxyethnal used as the solvent. Here, the molar concentration
of the precursor solution was 0.3M. Thereafter, the nitric acid was
added to have the same molar concentration as the precursor
solution. The resultant mixed solution for the oxide thin film was
stirred at a temperature of about 50.degree. C. at 300 rpm for 1
hour. The stirred oxide solution was stabilized for about a
day.
Comparison Embodiment
[0068] For comparison with the precursor solutions according to
embodiments of the inventive concept, acetic acid was used as a
stabilizer to form a precursor solution for IZO thin film by the
same method as the first embodiment.
[0069] Manufacture of Thin Film Transistor
[0070] Thin film transistors are formed using the precursor
solutions formed as described above.
[0071] A conductive material (e.g., molybdenum-tungsten (multi-mode
optical waveguide)) is deposited on a glass substrate with a
thickness of about 2000 .ANG. and then is patterned by a
photolithography process and an etching process to form a gate
electrode. Silicon oxide having a thickness of about 2000 .ANG. is
deposited by a chemical vapor deposition method to form a gate
insulating layer. The precursor solution formed according to the
aforementioned embodiments is deposited on the gate insulating
layer and then an annealing process is performed. Here, the
deposition of the precursor solution may be performed by a spin
coating method, a dip coating method, a ink jet printing method, a
screen printing method, a spray method, or a roll-to-roll method.
The annealing process after the deposition of the precursor
solution may use a furnace, a hot plate, or a rapid thermal
annealing method. The annealing process is performed at about
300.degree. C. for about 5 minutes. Subsequently, a conductive
material (e.g., tantalum) is stacked and then is patterned to form
a source electrode and a drain electrode.
[0072] Evaluation
[0073] FIG. 1 shows electrical characteristics of the thin film
transistor formed using the precursor solution for the IZO thin
film according to the first embodiment. Referring to FIG. 1, as
illustrated in a transfer curve of the transistor, a field effect
mobility is 2 cm.sup.2/Vs, a threshold voltage is 7V, a on/off
ratio is 2.5.times.10.sup.7, and a S-factor is 0.57 V/decade. On
the other hand, an output curve shows the function of the thin film
transistor which has a linear region and a saturation region surely
distinguished from each other.
[0074] FIG. 2 shows a result of an x-ray photoelectron spectroscopy
(XPS) of the IZO thin film formed using the precursor solution for
the IZO thin film according to the first embodiment. Referring to
FIG. 2, an indium (In) 3d5/2 peak is formed at a binding energy of
443.8 eV, and an In 3d3/2 peak is formed at a binding energy being
7.6 eV greater than 443.8 eV. Thus, it is confirmed that the IZO
thin film includes indium (In). And a zinc (Zn) 2p3/2 peak is
formed at a binding energy of 1021.45 eV, and a Zn 2p1/2 peak is
formed at a binding energy 23.1 eV greater than 1021.45 eV. Thus,
it is confirmed that the IZO thin film includes zinc (Zn).
Additionally, since a widely spreading peak is formed at a binding
energy of 530.5 eV, it is confirmed that indium (In) and zinc (Zn)
are oxidized. Furthermore, since the nitric acid stabilizer is
added into the oxide solution, the oxide solution has a very low
boiling point and does not include an organic material. Thus, an
organic material content (i.e., 0.7%) of the IZO thin film formed
using the nitric acid stabilizer is very smaller than that of the
IZO thin film formed using combination of monoethanolamine (MEA)
and acetic acid which is widely used in a conventional art. That
is, it is confirmed that the oxide solution including the nitric
acid is annealed to form the oxide thin film having a low organic
material content. Thus, electrical characteristics of the thin film
transistor may be improved. Additionally, it is confirmed that the
nitric acid-based stabilizer is one of important factors in the
manufacture of a low temperature-based oxide thin film
transistor.
[0075] FIG. 3 shows transfer curves of IZO thin film transistors
which are formed using the precursor solution of the first
embodiment under an annealing process of 250.degree. C. by
annealing apparatuses different from each other, respectively. A
tube furnace uses an annealing method using convection, a rapid
thermal annealing (RTA) apparatus uses an annealing method using
radiant heat, a hot plate uses an annealing method using heat
conduction, and a HTP uses an annealing method using a
high-pressure apparatus. Heat energy transmission by the conduction
is more effective than heat energy transmission by convection and
radiation. Additionally, since a density of the thin film increases
when a high pressure is applied, the electrical characteristics of
the thin film transistor may be improved. In the IZO thin film
transistor formed by the HTP, a mobility is 1.00 cm.sup.2/Vs, a
threshold voltage is 7.09, an on/off ratio is 7.78.times.10.sup.6,
and a gradient of a drain current (Id) is 0.53 V/decade.
[0076] FIG. 4 shows mobility of thin film transistors formed by
changing a molar ratio of zinc to indium. As a mole number of zinc
increases, the mobility of the tin film transistor increases. For
obtaining a conductive thin film, a IZO thin film deposited by the
spin coating method was annealed under a vacuum atmosphere at a
temperature of 250.degree. C. Since oxygen radical and hydroxyl
radical weakly combined with the residual organic material are
desorbed under the vacuum atmosphere, the IZO thin film has a very
high electron concentration of 10.sup.19 cm.sup.-3 or more.
[0077] FIG. 5 shows an electrical characteristic curve of an
aluminum oxide thin film which is formed by a precursor solution of
the third embodiment and a high-pressure annealing process
performed under an oxygen atmosphere at a temperature of
250.degree. C. A dielectric constant of the formed aluminum oxide
thin film was 9.8.
[0078] FIG. 6 shows an electrical characteristic curve of a thin
film transistor which includes the aluminum oxide thin film of FIG.
5 used as a gate insulating layer, and an oxide semiconductor
formed using the IZO solution of the first embodiment and stacked
on the aluminum oxide thin film. The thin film transistor has an
excellent characteristic of a field mobility of 13.3
cm.sup.2/Vs.
[0079] FIG. 7 shows electrical characteristic curves of the thin
film transistor formed by the second embodiment and the thin film
transistor formed by the comparison embodiment. The annealing
process was performed under the vacuum atmosphere at a temperature
of 200.degree. C. Referring to FIG. 7, a conductivity of the thin
film transistor formed using the nitric acid stabilizer according
to the inventive concept is greater than that of the thin film
transistor formed using acetic acid as the stabilizer.
[0080] FIG. 8 shows electrical characteristic curves of thin film
transistors formed using solutions which are formed by controlling
the composition ratio of indium to zinc in the second embodiment
within a range of 1:1 to 10:0. The annealing process was performed
under the vacuum atmosphere at a temperature of 200.degree. C. A
driving current of the thin film transistor increased in the
composition ratio of indium to zinc from 1:1 to 7:1. On the other
hand, the driving current of the thin film transistor reduced in
the composition ratio of indium to zinc from 7:1 to 10:0. An
optimized composition ratio of indium to zinc was 5:1 in the
embodiments, and the thin film transistor formed using the
optimized composition ratio had the mobility of 3.38 cm.sup.2/Vs,
the threshold voltage of 13.7, the on/off ratio of
1.4.times.10.sup.6, and the S-factor of 1.55 V/decade.
Additionally, in the output curve of the thin film transistor, the
linear region and the saturation region were surely distinguished
and the thin film transistor had a high saturation current. Thus,
the thin film transistor having excellent characteristics was
formed at a low temperature of 200.degree. C.
[0081] FIG. 9 shows a test result of stability with respect to a
remaining time of a thin film transistor formed by an oxide
solution having a composition ratio of indium to zinc of 5:1 and
not applied with a passivation layer. Referring to FIG. 9, as a
time passes, the threshold voltage moves a little toward a positive
direction, but the driving current of the thin film transistor may
not be greatly reduced. Additionally, when characteristic values of
the thin film transistor applied with the passivation layer, which
were measured 50 days later, may not be greatly different from
initial measurement values thereof. Thus, it is confirmed that the
stability of the thin film transistor is excellent.
[0082] In the embodiments described above, the oxide semiconductor
applied to the thin film transistor is described as an example.
However, the inventive concept is not limited thereto. The oxide
semiconductor according to inventive concept may be applied to
electronic devices needing a semiconductor thin film. For example,
the oxide semiconductor according to the inventive concept may be
used as materials of a resistor, a capacitor, an inductor, and/or a
diode and be applied to a display device (e.g., LCD and/or AMOLED)
or a solar cell including at least one thereof.
[0083] According to embodiments of the inventive concept, the oxide
semiconductor may be formed using the solution process, so that the
formation method may be simplified and formation costs may be
reduced.
[0084] According to embodiments of the inventive concept, the oxide
thin film may be formed by the low temperature process, so that it
is possible to form the electronic device capable of being applied
to a large area glass substrate and/or a flexible substrate.
[0085] While the inventive concept has been described with
reference to example embodiments, it will be apparent to those
skilled in the art that various changes and modifications may be
made without departing from the spirit and scope of the inventive
concept. Therefore, it should be understood that the above
embodiments are not limiting, but illustrative. Thus, the scope of
the inventive concept is to be determined by the broadest
permissible interpretation of the following claims and their
equivalents, and shall not be restricted or limited by the
foregoing description.
* * * * *